Prior art systems are known for storing and heating water in a plurality of storage tanks. For example, U.S. Pat. No. 5,027,749 (Cifaldi) teaches a multi-stage high efficiency gas fired water heater which includes a lower storage tank and upper recovery tank. Cold water is provided through an inlet into the recovery tank and heated water is removed via an outlet from the storage tank. Hot water from the top tank is supplied to the bottom tank via a conduit, and the top tank is, in turn, filled with cold water. The recovery and storage tanks are interconnected to transfer heated water from the recovery tank to the storage tank. Both tanks are heated to a maximum temperature during off-peak hours and the heated water is used during peak power consumption hours.
U.S. Pat. No. 4,438,728 (Fracaro) discloses three vertically stacked tanks. The upper tank has an incoming cold water inlet for directing incoming cold water toward the bottom of the tank. After the water is pre-warmed in the upper tank, the pre-warmed water passes out of the upper tank into the bottom of the intermediate tank. After further pre-warming in the intermediate tank, the water exits the intermediate tank and is directed toward the bottom of the lower tank. After reaching its hottest temperature in the lower tank, the hot water in the lower tank exits through the top of that tank.
Prior art systems are also known for enabling and disabling hot water heating coils in order to conserve energy consumption during peak power consumption hours. For example, published PCT international patent application number WO/PCT/US82/00756 (Vapor Corporation) discloses master and slave tanks which are disposed side-by-side and are controlled by a temperature controller and energized during "off-peak" hours by conventional controls to heat the storage fluid in both tanks to a high temperature.
It is well known that the peak power consumption hours occur on weekdays between, for example, 7:00 a.m. and 9:00 p.m., in many industrialized areas of the world, although the peak power consumption hours may vary from one location to another. Research indicates that one of the most significant contributors to peak power consumption is the well-known domestic hot water heater. Specifically, hot water consumption is maximized during the morning peak power consumption hours as a result of showers, washing etc., and in the evening peak power consumption hours through use of dish washing machines, laundry, etc.
Thermostat-controlled heating coils are often utilized to maintain the water temperature in a storage tank at a suitable level, and, once the temperature falls below that level, one or more heating coils are activated by the thermostats to increase the temperature to the present thermostat value, irrespective of the time of day.
It is known in the prior art to use timers and microprocessors for disabling thermostat-controlled hot water heaters at specific times. However, it in believed that such systems have only been used to enable or disable all of the thermostats at the same time, and not according to any predetermined sequencing of operation.
Since hydroelectric, nuclear and other electric power is generated at a continuous rate, there is considerable interest among federal-, provincial- and/or state-owned utilities to reduce power consumption during the peak power consumption hours and to defer the power consumption to off-peak hours.
There is no teaching or suggestion in the prior art systems of any means to separately heat multiple hot water tanks at different times during the off-peak hours. The systems of Cifaldi and Fracaro utilize structure which contemplates only heating both tanks simultaneously, albelt to different temperatures. Likewise, the PCT international application of Vapor Corporation teaches the use of two independent temperature controllers associated with two separate water heating tanks which are said to be energized during off-peak hours. However, there is no suggestion of enabling the two heaters for independent operation during off-peak hours for use in a hot water storage and delivery system. Such operation would not be consistent with the provision of lending energy to the water-based central heating system disclosed in the Vapor Corporation application.
Other general interest prior art is known, as follows:
European patent application number EP 0 104 362, French patent application number 2,486,212; British Patent No. 1,429,317; French patent application 2,507,749; DE 330478; U.K. patent application number GB 2,225,097; Canadian patent number 1,210,426; British patent number 218,796; British patent number 251,465; British patent number 580,061, U.S. Pat. No. 2,814,279, British patent number 1,358,996.